Burner

ABSTRACT

A burner used in conjunction with heat exchangers or furnaces has a chamber that is divided into a gas-mixing zone and a combustion zone, a means for axially introducing selected amounts of a relatively slow-flowing combustion supporting first gas into the mixing zone, a means for radially introducing selected amounts of a relatively rapid-flowing combustion supporting second gas as a plurality of gas streams into the gas mixing zone whereupon the first and second gases become intimately admixed, and a means in the combustion zone for igniting the admixed gases to generate hot exhaust gases for supplying heat to be stored in the heat exchanger or utilized otherwise.

United States latent 1 vietorisz 1 May 8,1973

[ BURNER [75] Inventor: Joseph A. Vietorisz, Pittsburgh, Pa. [7 3]Assignee: Koppers Company, Inc., Pittsburgh,

[22] Filed: Mar. 31, 1971 [21] Appl. No.: 129,868

[52] U.S. Cl. ..263/19 R, 431/352 [51] Int. Cl ..F23l 9/00 [58] Field ofSearch ..263/19; 431/2, 4,

[56] References Cited UNITED STATES PATENTS 3,227,202 1/1966 Morgan..239/431 X 3,574,508 4/1971 Rothhaar 3,244,220 4/1966 Kloecker ..431/5X 3,597,141 8/1971 Fracke et al ..431/353 3,267,927 8/1966 Hirschberg..239/431 X 5 gen Kinnisom ..431/2 Krapf ..263/19 PrimaryExaminer-Edward G. Favors Attorney-Fred C. Trenor, Oscar B. Brumback andOlin E. Williams A burner used in conjunction with heat exchangers orABSTRACT furnaces has a chamber that is divided into a gas-mixing zoneand a combustion zone, a means for axially introducing selected amountsof a relatively slow-flowing combustion supporting first gas into themixing 17 Claims, 6 Drawing Figures a 4 /5 0 25 27 z: 3/ 2 5 l9 j 2/Pmmmm 3,732,070

SHEET 2 BF 2 -J0.5E PH ,4. VIE Toe/5a I H15 AGE/LIT luveuroe.

FQED C REMbE H' I BURNER BACKGROUND OF THE INVENTION 1 Field of theInvention The invention relates to a heat exchanger for use inconjunction with a metallurgical furnace, and more particularly, to animproved gas burner disposed on the top of a blast furnace stoveforbuming combustible gases to produce hot exhaust gases that heat therefractory bodies in the stove.

Heretofore, blast furnace stoves have been comprised of four majorcompartments; the first being a vertical heat-storing chamber (referredto as the checkerwork chamber) containing a checkerwork arrangement ofheat-absorbing refractory bodies; the second being an adjacent verticalcombustion chamber (referred to as the combustion chamber) in which fuelgas or the like is burned to generate hot gases for heating therefractory bodies in the checkerwork chamber; and the third being adome-shaped chamber (referred to as the dome) at the top of both thecheckerwork and combustion chambers, and the fourth being a plenumchamber below the checkerwork chamber in which the combustion productsare collected or the cold blasts of air are distributed. A partitionwall divides the combustion chamber from the checkerwork chamber.

In operation of the above-described blast furnace stove mixtures of fuelgas and air are admitted into, ignited and burned within the combustionchamber to generate hot, exhaust gases. The hot, exhaust gases,generated in the combustion chamber, flow upwardly through thecombustion chamber, through the dome, and flow downwardly through thecheckerwork chamber to heat the refractory bodies therein. After enoughheat has been stored in the refractory bodies, the gas burning isstopped, and cold blasts of air, admitted at the bottom of thecheckerwork chamber,

ascend upwardly through the checkerwork chamber,

and the air is gradually heated to a selected hot blast temperature; innewer furnaces the temperature is about 2000F. The heated air passesthrough the dome and descends downwardly through the combustion chamberto the hot blast main and thence to the blast furnace.

Blast furnace operators have proved the theory that higher blast airtemperature increases the production rate of a blast furnace.Accordingly, the temperatures in the blast furnace stoves have beenincreased; however, the above-described conventional blast furnace stoveis not best suited to operate at prolonged temperatures in excess of2000F. as several serious problems may occur. For example, the partitionwall may become over-stressed by higher operating temperatures in excessof 2000F., and, consequently, cracks develop in the partition wallwhereby cold blasts of air by-pass the heated refractory bodies in thecheckerwork chamber. Also, the refractory bodies near the dome areheated to higher temperatures than the refractory bodies more remotefrom the dome. Consequently, the refractory bodies near the dome requirea greater refractoriness than those refractory bodies remote from thedome. conventionally, the checkerbricks having a high alumina contentare used in the top layers of the blast furnace stove; the percentage ofalumina is higher for increased blast temperatures. The cost of usingbricks having a very high percentage of alumina is prohibitive of theiruse. However, only bricks having the high percentage of alumina canraise the softening point of such bricks over and beyond thetemperatures to which they are exposed when the stove is to provide hotblast line temperatures well in excess of 2000F. Recently, silica brickshave been experimentally used near the dome because of their higherrefractoriness. The temperatures in such blast furnace stoves must bemaintained during their full service life at temperatures above thetemperature at which silica bricks undergo detrimental crystallographicchanges in order to maintain the integrity of the silica bricks.

2. Description of the Prior Art Several solutions to the foregoingproblems have been attempted. One solution has been to isolate both thecombustion chamber from the checkerwork chamber in separate shells andto connect them together with a flue that has properly designedexpansion joints. This solution has been too expensive because theexterior combustion chamber requires an additional long stack, linedwith an insulating refractory for adequate insulation to minimize theheat losses, and because of the specially designed expansion joints thatcan adjust to the differences in the thermal expansion of the twoconnected chambers during the operation of the stove. Another solutionhas been to modify the combustion chamber and to provide merely acheckerwork chamber and to modify the dome at the top thereof byproviding a burner around or above the dome in which fuel gas and airare burned to generate hot, exhaust gases for heating the refractorybodies in the checkerwork chamber, often called top firing".

Various burner arrangements have been proposed for the top firing ofblast furnace stoves. For example, in U. S. Pat. No. 3,473,793, air andfuel gas are admixed in an annular chamber around the modified dome ofthe stove wherefrom the mixed gases move upwardly through a number ofslits into the dome. The mixed gases are burned in the dome to producehot, exhaust gases. The hot, exhaust gases then travel downwardly fromthe dome into the checkerwork chamber. The burning gases flow generallyupwardly and the burnt gases flow generally downwardly. The counter flowof burning and burnt gases may result in unstable and incompletecombustion. In U. S. Pat. No. 3,380,723, air and fuel gas are admixed ina frustoconical chamber situated on top of the blast furnace stove. Theair is introduced axially into the chamber and the fuel gas isintroduced tangentially into the chamber through a single port wherebythese gases are admixed and are burned in the chamber to produce hot,exhaust gases. The flame of the burning mixed gases undergo anindistinct, conical, swirling movement that will save the lining fromscouring, however, the gases will tend to leave the center of thecombustion chamber; consequently, the combustion of the mixed gases isnonuniform throughout the cross-section of the frusto-conical chamber.Ultimately, the refractory bodies in the checkerwork chamber may not beheated uniformly by the hot exhaust gases and the uniform and efficientheating of cold blasts of air may be decreased. In both patents therefractory linings of the burners do not merge smoothly with or share acommon tangent with the refractory linings of the stove. Above the stoveat the inner surface of the conical dome the flow of the burning andburnt gases will be particularly turbulent resulting in gas temperaturesand pressures that are not well-balanced unless the included angle ofthe cone is quite small i.e., unless the cone is exceedingly long.

The present invention relates to an improved burner design that providesmore stable combustion and wellequalized temperatures and pressures inthe burner. The burner of the present invention is made from refractorybodies and, hence, water-cooling the various members of the burner isunnecessary. An intimate mixture of the air and fuel gas is achieved inmybumer and the distances the flame travels are greatly reduced wherebya more uniform burning of the mixed gases occurs. Smooth expansion andflow of burnt gases are secured by using specially shaped combustionzone contours. The introduction of all the combustion supporting gasesis symmetrical about the central axis of the burner; consequently,localized hot spots in the dome are eliminated.

SUMMARY OF THE INVENTION In accordance with the invention a burner foruse with heat exchangers or furnaces comprises a burner chamber that,when disposed at the top of the stove, is symmetrically arranged aboutthe central vertical axis of the stove, a first conduit communicatingwith the top of the burner chamber for carrying a combustion-supportingfirst gas and for axially introducing the first gas at relatively lowvelocities into the burner chamber, a header surrounding a portion ofthe burner chamber for receiving a combustion-supporting second gas, asecond conduit communicating with the header for carrying the secondgases and for introducing the second gases into the header, a burnerring between the burner chamber and the header having a plurality ofgenerally radially extending conduits through the ring for radiallyintroducing a plurality of streams of the second gas at relatively highvelocities into the burner chamber, whereby the first and second gasesbecome intimately admixed in the burner chamber, means in the burnerchamber for igniting the first and second gases whereby the admixedgases are burned to produce hot, exhaust gases for heating therefractory checkers in the blast furnace stove.

GENERAL DESCRIPTION OF THE DRAWINGS In the drawings: FIG. 1 is avertical sectional view of the dome portion of a blast furnace stoveillustrating an embodiment of the burner of the invention;

FIG. 2 is a top view ofa segment of the burner ring of FIG. 1;

FIG. 3 is a cross-sectional view of the burner ring segment of FIG. 2taken at line III-III;

FIG. 4 is a top isolated view of the burner ring of FIG. 1;

FIG. 5 is a top isolated view of another embodiment of the burner ringof FIG. 4; and

FIG. 6 is an isometric view of a segment of the burner ring of FIG. 1.

DETAILED DESCRIPTION In FIG. 1 the top portion of a blast furnace stove11 includes a checkerwork chamber 13, a dome 15 at the top of thechamber 13 and an embodiment of the improved burner 17 in accordancewith the invention.

Chamber 13 has a metal shell 19 that has an internal refractory andinsulating lining 21 and chamber 13 contains a quantity of conventionalheat-absorbing refractory bodies or bricks 23, referred to ascheckerwork". The refractory bodies 23 are capable of being heated andof storing heat and, therefore, of imparting such stored heat to a blastof cold air which is introduced into the blast furnace stove in aconventional manner.

The dome 15, at the top of chamber 13, has a metal shell 25 and aninternal refractory and insulating lining 27 that defines a chamber 28.Dome 15 preferably has hemispherical shape or configuration. The dome 15is supported by brackets 31 that are fixed to shell 19 so that the domeis independent of the radial thermal movements of shell 19. As shown inFIG. 1 the refractory lining 27 of dome 15 is laterally adjacent to andoverlaps refractory lining 21 of chamber 13. This arrangement isdesirable since it permits a free axial thermal movement of therefractory bricks 23 and refractory lining 21 up into dome 15, withoutexerting thermal forces on the domes refractory lining 27.

A conventional nozzle 29 having a metal shell 35 and an internalrefractory and insulating lining 37 extends from a side of the dome 15,as shown in FIG. 1. This nozzle 29 conveys the hot blast of air, heatedin chamber 13, through conventional valve 39 and conduit 41 to aconventional hot blast main (not shown).

In accordance with the invention, burner 17, as illustrated in FIG. 1,is situated on top of dome 15 and has a metal shell 43 and an internalrefractory and insulating lining 45 that defines a chamber 47 for mixingand burning air and fuel gas. Chamber 47 is divided into an uppergas-mixing zone A inwhich the combustible gases are intimately admixed,and a lower combustion zone B in which the mixed gases are burned. Theburner includes a first aperture 49 at its top for axially receivingcombustion supporting first gas (preferably an enriched premixture offuel gas and air) into chamber 47, a second aperture 51 at its side forradially receiving a combustion supporting second gas (preferably air),an annular channel or header 53 communicating with the second aperture51, and, a burner ring 55 communicating with the annular channel 53 andthe gas-mixing zone A of chamber 47.

Burner chamber 47 may have any cross-sectional configuration thatincreases downwardly in the direction of gas flow as shown in FIG. 1;however, the internal surface of the refractory lining 45 of burner 17has generally a curved contour 64 that merges smoothly with therefractory lining 27 of dome 15 so that the refractory linings 45 and 47share a common tangent whereby a smooth flow of gases from the burner tothe dome is achieved.

The curved contoured downwardly increasing crosssectional configurationof chamber 47 is an advantageous feature of the invention. As the gasesare burned therein the volume of the gaseous products of combustionincrease and the downwardly increasing cross-sectional configuration ofthe chamber allows ex- The annular channel 53 receives the secondcombustible supporting gas and uniformly distributes it around theburner ring 55.

The burner ring 55 is composed of a refractory material and, asillustrated in FIGS. 1 and 2, includes a plurality of conduits or ports57 that extend entirely through the ring, and that communicate with thegasmixing zone A of burner chamber 47. The conduits 57 are superimposedone above the other in a vertical direction, being parallel to eachother as illustrated in FIG. 1. If desired, however, the conduits 57need not be arranged in a parallel fashion in the vertical direction.Conduits in two elevations are shown in FIG. 1; however, more conduitsin more than two elevations ma be used as desired.

In FIG. 3 the conduits 57 are downwardly inclined at an angle (a) inrespect of line dd drawn perpendicularly to the vertical central axis CCof chamber 47. This angle may vary, and the conduits 57 may be inclinedeither upwardly or downwardly at angles from 0 to 45 with respect toline d-d. The angle (a) is selected to suit the fuel characteristics andheating requirements of the burner.

The conduits 57 in the drawings are radially arranged with respect tothe burner ring 55 and to each other so that the centerlines of theconduits converge at a common axis 0 in FIG. 2 and that is thecenterline of the burner in FIG. 4 so that the gases issuing from eachconduit travel the same distance to reach the common axis. When all thecenterlines of each conduit are so arranged, the velocity of the gasstreams issuing from the respective conduits 57 will be the same at thecommon axis because all of the gas streams travel the same distance toreach the axis. Equal gas velocities at the common axis is a desirablefeature of the invention as it encourages a more uniform combustion ofthe mixed gases in chamber 47. If desired, however, the conduits may beeccentrically arranged with respect to the burner ring and to each otherso that the centerlines of each conduit are tangent to a circle ofeccentricity, and again, the gases issuing from each conduit travel thesame distance to the circle of eccentricity.

The burner ring 55, as shown in FIG. 3, has a top surface 59, a bottomsurface 61, an inside surface 63 and an outside surface 65. The top andbottom surfaces 59 and 61 are planar and, as shown herein, are parallelto each other so that the burner ring may easily be installed into thecutaway section 54 of the burner 17. The inside surface 63 as shown inFIG. 3, is a frustoconical surface and the elements of this surface arealso coextensive with the elements of the internal surface of therefractory lining 45, thereby providing a smooth, unbroken flow of gasesthrough the burner 17 as shown in FIG. 1. The inside surface 63 divergeswith respect to the central axis CC so that the cross-section of theburner ring 55 increases downwardly in the direction of gas flow for thepurposes previously described. The burner ring 55 is so constructed thatit may be independently removed and installed in the burner 17. For thispurpose, a manhole 67 is provided in the side of burner 17 so that theburner ring 55 is accessible from the outside of the blast furnace dome15, as shown in FIG. 1. More than one such manhole may be provided ifdesired.

The burner ring 55, illustrated in FIGS. 4 and 5, is made of foursegments (69, 71, 73 and 75) and each segment as shown comprises aquarter section of the ring 55. The ring 55, however, may be comprisedof other than four sections, if desired, and may have otherconfigurations such as an oblong or an oval shape or the like. In FIG. 4the ring segments 69-75 are all equidistant from the central axis (C-C)of the chamber 47 so that the inside surface 63 of each ring segment isequidistant from the central axis (CC) of the burner 17. In thisposition the conduits are radially arranged so that their centerlinesconverge at the central axis of the chamber 47.

In FIG. 5 the embodiment of the burner ring is shown where each segment(69-75) is eccentrically arranged with respect to the central axis (CC)of the chamber 47 and the inside surfaces 63 of the adjacent ringsegments are not equidistant from the central axis (CC In this positionthe centerlines of each conduit 57 of each segment converge at a commonaxes (a, b, c, d) but each common axis is equally eccentric to thecentral axis (CC) of the chamber 47. The gas streams issuing from theconduits 57 into chamber 47 converge at a location eccentric to thecentral axis of the chamber and thereby they effect a swirling action ofthe gases, as shown in FIG. 5.

FIG. 1 shows a conventional pilot burner 77 that is directed toward thecombustion zone B of the chamber 47 for igniting the gases which havebeen admixed in the gas-mixing zone A. An ignition port 79 is providedin the side of the burner 17 for lighting the pilot burner 77.

The combustion supporting first gas is conveyed through a conventionalfeed conduit 95, through a conventional stop valve 97 and through aconventional flow regulating device 99 into an increaser 101. Increaser101 has a metal shell 103 and an internal refractory lining 105. Theincreaser 101 is generally frustoconical with the smaller end connectedto the flow regulating device 99 and with the larger diameter connectedto a mixer conduit 89, described hereinafter. The increaser 101 preventsany backfiring from occurring within the flow regulating device 99.Consequently, the flow regulator 99 and the stop valve 97 need not bewater cooled as the combustion of the first gas can not occur in theincreaser 101 nor are they exposed to intense heat radiation. Theincreaser may have a nozzle 113 in its side, if desired, for theadmission of an enriching gas having a higher heating value than thefirst gas. Such enriching gases may include coke oven gas, natural gas,and the like. The enriching gas boosts the flame temperature of theburning mixture of gases occurring in the burner 17 and increases theheat input into the checkerwork chamber.

Increaser 101 engages the mixer conduit 89, as shown in FIG. 1, which isan optional feature of the invention. The mixer conduit has a metalshell 91 and an internal refractory lining 93 that has the same innerdiameter as the adjacent refractory lining 105 of the increaser. Thus,there is a smooth flow of the first gases from the increaser through themixer conduit. Companion flanges 107 and 109 of the increaser and mixerconduit engage each other and are secured together with fasteners (notshown) such as bolts. The mixer conduit 89 axially receives the firstgases from the increaser 101 and tangentially receives a portion of thesecond gases (preferably air called primary air) from conduit 1 1 1, asshown in FIG. 1. The first gases and the portion of the second gases areintimately premixed in the mixer conduit 89 to provide a gas premixturesince the portion of second gases enter the mixer tangentially to effecta swirling movement of the gases. This premixing is a desirable featureof the invention in that it effectively speeds up the combustion thatsubsequently occurs in burner 17.

An elbow 80 is situated on top of burner 17, engaging mixer conduit 89and communicating with the first aperture 49 of the burner 17 as shownin FIG. 1. The elbow 80 having a metal shell 81 and an internalrefractory lining 83 has a flange 85 at one end that engages flange 62of burner 17. The elbow 80 also has a flange 82 at its other end thatengages flange 108 of the mixer conduit 89 so that elbow 80 is removablefrom the burner whereupon workman may enter the burner for repairworkand the like. Fasteners (not shown) such as bolts are used to secure theelbow to the burner and the mixer conduit.

During the operation of the burner 17 the refractory lining 83 willabsorb some radiated heat from the combustion of the mixed gases and,consequently, the heat in the refractory lining 83 will tend to preheatthe premixed gases flowing through the elbow which will desirably resultin slightly higher flame temperatures in the burner when the finalmixture of gases is burned. A desirable feature of the elbow 80 is thatits refractory lining 83 merges smoothly with refractory lining 93 ofthe mixer conduit 89 at one end and with refractory lining 45 of burner17 at the other end so the gases pass therethrough smoothly.

The second combustion supporting gas, usually air, is conveyed through afeed conduit 115 toward burner 17, as shown in FIG. 1. At a tee-section117 in the feed conduit 1 15, the air may be split into primary air andsecondary air in the preferred embodiment of the invention bychannelling the primary air into conduit Ill and the secondary air intoa conduit 119. The primary air" in the conduit lll passes through stopvalve 121 and a regulating device 123, and the secondary air" passesthrough stop valve 125 and a regulating device 127, as shown in FIG. 1.The regulating device 123 keeps the flow of "primary air through conduit111 at a level such that the premixture of primary air and fuel gas inmixer conduit 89 is below the flammable range. Stop valve 121 can shutoff the supply of primary air" altogether if desired.

The secondary air passes through conduit 1 19, increaser 129, nozzle 131and thence in to annular channel 53, as shown in FIG. 1 whereupon thesecondary air is uniformly distributed around burner ring 55 aspreviously described. The increaser 129 has an increasing diameter inthe direction of gas flow so as to prevent backfiring of gases in theburner 17 from occurring in flow regulating device 127. Both theincreaser 129 and the nozzle 131 have a metal shell 133 and an internalrefractory lining 135.

In the operation of the preferred embodiment of the burner of theinvention, blast furnace gas is admitted into conduit by valve 97,natural gas is admitted through nozzle 113 into increaser 101 and air isadmitted into conduit whereupon a portion of the air (primary air)passes through conduit 11] into mixer conduit 89. The primary airtangentially enters mixer conduit 89 and becomes admixed with the blastfurnace gas and the natural gas and causes the premixed gas to undergo aswirling direction in FIG. 1 in a clockwise direction as viewed from theincreaser 101 to the burner 17. The other portion of the air (secondaryair) passes through increaser 129, nozzle 131 into header 53 andeventually into the gas-mixing zone (A) of the burner as a plurality ofstreams at relatively high velocities. In one embodiment of theinvention the streams of secondary air enter the gas-mixing zoneradially; in another embodiment the streams enter the gas-mixing zoneeccentrically of its central axis CC so that the gases will whirl aboutthe axis as shown in FIG. 5 in a counter-clockwise direction. Bydisposing the conduits or segments in the opposite direction, aclockwise whirling action of the gases may be achieved. Very intimateadmixing will be obtained in any case by shearing and entrainment of theradially flowing secondary air at high velocities in the premixed gaseswhich flow swirling downwardly at relative low axial velocities. Thepremixed gases entering the chamber axially may swirl in an oppositedirection of the secondary air radially entering the chamber so that agood homogeneous admixture of the gases is achieved in the gas-mixingzone.

The novel mixing action above described results in a short flame lengthin the burner, and in the rapid combustion of the mixed gases so that noflame propagates into the top bricks in the checkerwork chamber.Advantageously, complete combustion occurs in a relatively short time inthe gas burning chamber even when non-enriched blast furnace gas isbeing used (which is known to have a low rate of flame propagation). Ofcourse, the respective flow rates of the blast furnace gas and of thesecondary air into the gas mixing zone A of chamber 47 may be regulatedto provide the desired heat release. It is postulated that the axialflow velocity of blast furnace gas be less than the radial, or nearradial flow velocity of secondary air into the gas mixing zone ofchamber 47 as this provides the thorough admixing and short flamelengths and permits sufficient time for complete combustion entirelywithin the burner and the dome.

A substantial part of the heat generated by the combustion of the mixedgases is absorbed by the refractory bodies in the checkerwork chamber 13and the burner is operated until the refractory bodies have absorbedenough heat to preheat a cold blast of air to the required temperaturefor a preset period of time for use in the blast furnace.

After the refractory bodies in the checkerwork chamber 13 have beensufficiently heated, valves 97,

121 and 125 are closed to terminate the burning of gases in the burner.Subsequently, cold blasts of air are admitted into the bottom of thecheckerwork chamber 13 (not shown) which pass upwardly through thecheckerwork chamber gradually being heated to the required temperatures,then, exit the checkerwork chamber through nozzle 29, valve 39 andconduit 41 to enter blast furnace via the hot blast main (not shown).

A feature of the invention is that fuel gas and air may be usedinterchangeably. As contemplated in the drawings fuel gas is axiallyintroduced and air is radially introduced into the burner, however, theburner of the invention is so constructed that air may be axiallyintroduced and fuel gas radially introduced into the burner,

An optional feature of the invention is illustrated in FIGS. 3 and 6. Anembodiment of a control device or shutter 137 is shown for closing orshutting off or opening some of the conduits 57 to adjust the flowvelocities of the secondary air through the conduits 57 into thegas-mixing zone A of burner chamber 47. to accommodate widely varyingburning rates. The shutter 137 in its embodiment described hereincomprises a frustoconical plate 139 that extends around burner ring 55as shown in FIG. 6. The plate 139 fits in a cutaway section 149 of theoutside surface 65 of the burner ring 55 and is movable along thecircumference thereof. The plate 139 has a plurality of apertures 143that have an inverted -L shape as shown in FIG. 6. The plate 139 is tobe moved manually; however, it could be moved automatically, if desired.The plate. 139 in FIG. 6 is in a position in which all of the conduits57 are open. By moving plate 139 to the right a specified distance allof the upper conduits will be closed while the lower conduits willremain open. A desirable feature of the shutter 137 is that the shutteris situated on the outside surface 65 of the burner ring where it is notexposed to direct thermal radiation but is protected by the refractoryring 55 and is accessible for adjustment from manholes 67.

It will be recognized that the shutter 137 may be greatly modified toprovide different arrangements for shutting off the conduits 57. Forexample, apertures other than L-shaped apertures, may be used, or theshutter may be moved axially rather than circumferentially to shut offor to open the conduits. The important feature of any modifiedembodiment of shutter 137 is that a number of conduits, preferablysymmetrically located, may be rendered inactive for reduced secondaryair supply to obtain desired flow velocities of secondary air into thegas-mixing zone A of burner chamber 47 and that the shutter 137 isprotected from thermal radiation. Strategically located observationports and thermo wells may be provided for effective control (notshown).

Although the present invention has been illustrated with a singleembodiment, it will be understood that it is illustrative of theinvention and by no means restrictive thereof. Those skilled in the artwill readily recognize that the invention can be applied not only on thetop of a heat exchanger but in any position in conjunction with anyfurnace. Therefore, numerous modifications can be made within the scopeof the invention without deviating from the spirit of the followingclaims or without sacrificing their advantages.

What is claimed is:

1. A burner for a top-fired blast fumace stove that has a checkerchamber and a dome at the top thereof comprising:

a. a burner chamber that is disposed at the top of said dome and that issymmetrically arranged about the central vertical axis of said dome;

a first conduit communicating with the top of said burner chamber forcarrying a combustion-supporting first gas and for axially introducingsaid first gas at relatively low flow velocities into said burnerchamber;

c. a header completely surrounding a portion of said burner chamber forreceiving a combustion-supporting second gas;

a burner ring between said burner chamber and said header having aplurality of generally radially extending conduits through said ring forradially introducing at relatively high flow velocities a plurality ofstreams of said second gas inwardly into said burner chamber;

e. a second conduit communicating with said header for carrying saidsecond gases and for introducing said second gases into said header;

f. means in said burner chamber for igniting the first and second gaseswhereby the first and second gases become intimately admixed in saidburner chamber and said admixed gases are burned to produce hot, exhaustgases.

2. The burner of claim 1 including an increaser in operative associationwith said first conduit for preventing the backfiring of any gases intosaid first conduit; said increaser having an increasing size in thedirection of gas flow therethrough.

3. The burner of claim 1 wherein said first gas is a fuel gas and saidsecond gas is air.

4. The burner of claim 3 including a nozzle in said increaser forintroducing an enriching gas into said increaser for admixture with saidfuel gas passing therethrough; said enriching gas having a heating valuegreater than said fuel gas.

5. The burner of claim 1 including a mixer conduit in operativeassociation with said first conduit; said mixer conduit having a meansfor tangentially receiving a portion of said second gases whereby saidfirst gases passing axially through said mixer conduit are intimatelyadmixed with said second gases tangentially entering said mixer conduit.

6. The burner of claim 1 including an increaser in operative associationwith said second conduit for preventing the backfiring of any gases intosaid second conduit; said increaser having an increasing size in thedirection of gas flow therethrough.

7. The burner of claim 5 including a means in operative association withsaid second conduit for diverting a portion of said second gases to saidmixer conduit and for diverting the other portion of said second gasesto said header.

8. The burner of claim 1 including manholes in said burner chamber forexterior access to said burner ring.

9. A burner for use in conjunction with high temperature heat exchangersor furnaces comprising:

a. a chamber having i. a gas-mixing zone, and ii. a combustion zone;

b. means for introducing a combustion supporting first gas generallyaxially of said chamber into said mixing zone at relatively low flowvelocities;

c. said gas mixing zone including i. a burner ring that is comprised ofa plurality of refractory segments; said ring segments having aplurality of generally radially arranged conduits that are inclined atan angle with respect to the central axis of said chamber forintroducing a combustion-supporting second gas generally radially ofsaid chamber into said mixing zone at relative high flow velocitieswhereupon said first and second gases become intimately admixed in saidgas mixing zone; and

. a header surrounding said ring for receiving and distributing saidsecond gases into said conduits; and

d. means in said combustion zone for igniting said admixed gases.

10. The burner of claim 9 wherein said angle is from 045 upwards ordownwards from the plane perpendicular to said axis.

1 l. The burner of claim 9 wherein each conduit is eccentricallyarranged with respect of the central axis of said chamber so that saidsecond gas passing through said conduits enter said mixing zone at alocation eccentric to said axis to effect a swirling action of the firstand second gases in said mixing zone.

12. The burner of claim 9 including means for regulating the flowvelocities of said second gases into said mixing zone.

13. The burner of claim 9 wherein said first gas is a fuel gas and saidsecond gas is air.

14. The burner of claim 13 including means for enriching said fuel gaswith an enriching gas having a higher heating value than said fuel gasprior to its entry into said gas-mixing zone.

15. The burner of claim 9 wherein said first gas is air and said secondgas is a fuel gas.

16. The burner of claim 9 wherein said chamber has a diameter thatincreases in the direction of gas flow therethrough so that as saidadmixed gases are ignited and burned their expansion may be accomodatedeffectively within said chamber whereby the combustion will be smoothlycompleted before the gases enter into said heat exchanger or furnace.

17. The burner of claim 9 including means for premixing said first gaseswith a portion of said second gases before said first gas enters saidgas-mixing zone.

1. A burner for a top-fired blast furnace stove that has a checkerchamber and a dome at the top thereof comprising: a. a burner chamberthat is disposed at the top of said dome and that is symmetricallyarranged about the central vertical axis of said dome; b. a firstconduit communicating with the top of said burner chamber for carrying acombustion-supporting first gas and for axially introducing said firstgas at relatively low flow velocities into said burner chamber; c. aheader completely surrounding a portion of said burner chamber forreceiving a combustion-supporting second gas; d. a burner ring betweensaid burner chamber and said header having a plurality of generalLyradially extending conduits through said ring for radially introducingat relatively high flow velocities a plurality of streams of said secondgas inwardly into said burner chamber; e. a second conduit communicatingwith said header for carrying said second gases and for introducing saidsecond gases into said header; f. means in said burner chamber forigniting the first and second gases whereby the first and second gasesbecome intimately admixed in said burner chamber and said admixed gasesare burned to produce hot, exhaust gases.
 2. The burner of claim 1including an increaser in operative association with said first conduitfor preventing the backfiring of any gases into said first conduit; saidincreaser having an increasing size in the direction of gas flowtherethrough.
 3. The burner of claim 1 wherein said first gas is a fuelgas and said second gas is air.
 4. The burner of claim 3 including anozzle in said increaser for introducing an enriching gas into saidincreaser for admixture with said fuel gas passing therethrough; saidenriching gas having a heating value greater than said fuel gas.
 5. Theburner of claim 1 including a mixer conduit in operative associationwith said first conduit; said mixer conduit having a means fortangentially receiving a portion of said second gases whereby said firstgases passing axially through said mixer conduit are intimately admixedwith said second gases tangentially entering said mixer conduit.
 6. Theburner of claim 1 including an increaser in operative association withsaid second conduit for preventing the backfiring of any gases into saidsecond conduit; said increaser having an increasing size in thedirection of gas flow therethrough.
 7. The burner of claim 5 including ameans in operative association with said second conduit for diverting aportion of said second gases to said mixer conduit and for diverting theother portion of said second gases to said header.
 8. The burner ofclaim 1 including manholes in said burner chamber for exterior access tosaid burner ring.
 9. A burner for use in conjunction with hightemperature heat exchangers or furnaces comprising: a. a chamber havingi. a gas-mixing zone, and ii. a combustion zone; b. means forintroducing a combustion supporting first gas generally axially of saidchamber into said mixing zone at relatively low flow velocities; c. saidgas mixing zone including i. a burner ring that is comprised of aplurality of refractory segments; said ring segments having a pluralityof generally radially arranged conduits that are inclined at an anglewith respect to the central axis of said chamber for introducing acombustion-supporting second gas generally radially of said chamber intosaid mixing zone at relative high flow velocities whereupon said firstand second gases become intimately admixed in said gas mixing zone; andii. a header surrounding said ring for receiving and distributing saidsecond gases into said conduits; and d. means in said combustion zonefor igniting said admixed gases.
 10. The burner of claim 9 wherein saidangle is from 0-45* upwards or downwards from the plane perpendicular tosaid axis.
 11. The burner of claim 9 wherein each conduit iseccentrically arranged with respect of the central axis of said chamberso that said second gas passing through said conduits enter said mixingzone at a location eccentric to said axis to effect a swirling action ofthe first and second gases in said mixing zone.
 12. The burner of claim9 including means for regulating the flow velocities of said secondgases into said mixing zone.
 13. The burner of claim 9 wherein saidfirst gas is a fuel gas and said second gas is air.
 14. The burner ofclaim 13 including means for enriching said fuel gas with an enrichinggas having a higher heating value than said fuel gas prior to its entryinto said gas-mixing zone.
 15. The burner of claim 9 wherein Said firstgas is air and said second gas is a fuel gas.
 16. The burner of claim 9wherein said chamber has a diameter that increases in the direction ofgas flow therethrough so that as said admixed gases are ignited andburned their expansion may be accomodated effectively within saidchamber whereby the combustion will be smoothly completed before thegases enter into said heat exchanger or furnace.
 17. The burner of claim9 including means for premixing said first gases with a portion of saidsecond gases before said first gas enters said gas-mixing zone.